PHYSICOCHEMICAL JUSTIFICATION OF OPTIMAL THERMAL ACTIVATION AND DISPERSITY PARAMETERS OF KARA-KECHE CLAY FOR THE PRODUCTION OF AN ACTIVE MINERAL ADDITIVE

Introduction. One of the key areas for improving the environmental efficiency of cement materials is the reduction of the clinker component. Therefore, reducing the clinker fraction is regarded as one of the key approaches to improving the environmental efficiency of cement-based materials. Among such materials, kaolinite-containing and polymineral clays are of particular interest because firing causes dehydroxylation of clay minerals, breakdown of the original ordered structure, and formation of a reactive amorphous aluminosilicate phase. Another important parameter is the degree of dispersity after heat treatment. Fine grinding changes the specific surface area and accessibility of reactive sites. For this reason, selecting the optimal thermal activation and dispersity parameters should be treated as an independent scientific task that precedes evaluation of the additive in cement systems. In this regard, the aim of the present study was to provide a physicochemical justification of the optimal thermal activation and dispersity parameters of Kara-Keche clay for producing an active mineral additive. Materials and Methods. The object of the study was kaolinite-containing clay from the Kara-Keche de-posit (Kyrgyz Republic). The chemical composition, phase assemblage, and microstructural features of both raw and calcined samples were characterized using WDXRF, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results. This study investigates the phase transformations and microstructural evolution of Kara-Keche clay during thermal activation followed by fine grinding in order to determine the optimal processing parameters for producing an active mineral additive. The studied clay was identified as a kaolinite-illite-quartz type material. Heat treatment at 700 °C led to a more reactive state due to the dehydroxylation of kaolinite and an increase in the amorphous aluminosilicate fraction. The most favorable ratio of amorphous to crystalline phases was achieved after 2 min of grinding, corresponding to a specific surface area of 900-1200 m2/kg. Extending the grinding time to 3 min reduced the specific surface area to 700-850 m²/kg and was accompanied by partial recrystallization and a 1.5-2-fold increase in mullite content, result-ing in lower reactivity of the thermally activated clay. Conclusions. The results of the conducted studies indicate the possibility and potential of using clay from the Kara-Keche deposit as a raw material base for the production of active mineral additives. The results can be applied to the development of technologies for producing active mineral additives from locally available clay raw materials.